Paper detail

Multi-Lepton Events at HERA

The analysis of events containing multiple high Pt leptons (electrons and muons) produced in ep collisions has been performed with the H1 and ZEUS detectors at HERA, using the full data sets collected by the experiments in the period 1994-2007. Mutually exclusive event topologies containing at least two charged leptons are analysed. The H1 and ZEUS data, corresponding to a total integrated luminosity of about 1 fb^-1, are combined in a common phase space. The observed event yields are compared to the predictions from the Standard Model. In general a good agreement is found, where the expectation is dominated by photon-photon collisions. Interesting events at high mass and high Pt are observed by both experiments. The total and differential cross sections for multi-lepton production at HERA are also measured.